If the MAF is dirty, the fix is easy enough: just clean or replace the MAF sensor. If the MAF sensor is dirty, the fuel trim at idle will probably be close to normal (plus or minus 3 to 5 range), but as engine speed increases up to 2500 RPM, you will see the fuel trim value go positive (5 or higher). One way to diagnose a dirty MAF sensor is to hook up a scan tool, choose the PID data menu and look at fuel trim values while the engine is running.
#Ol fault 2003 mazda 6 p0171 code#
As a result, the engine runs lean and sets a P0171 and/or P0174 code (see Ford TSB 98-23-10 for details). This causes the MAF sensor to under report airflow, which in turn misleads the powertrain control module (PCM) so it doesn't add enough fuel to maintain a properly balanced air/fuel ratio. The vapors can leave a waxy coating on the sensor wire. The MAF sensor can also be contaminated by fuel vapors that back up through the intake manifold and throttle body when the engine is shut off. Dirt can stick to the MAF sensor wire and form a coating that slows the response of the sensor to changes in airflow.
The MAF sensor should be protected from outside dust and debris by the air filter, but sometimes the air filter doesn't fit real tight inside the housing and allows unfiltered air into the engine. The MAF sensor is located in the air inlet tube just ahead of the throttle body. One of the most common causes of Ford P0171 and P0174 lean codes is a dirty mass airflow (MAF) sensor.
If the problem is not enough fuel, the underling cause may be a weak fuel pump, restricted fuel filter, leaky fuel pressure regulator or dirty fuel injectors.Ĭleaning or replacing the sensor should make the code go away. Unmetered air can enter the engine through a vacuum leak, a dirty airflow sensor that is not reading airflow accurately, an EGR valve is not closing and is leaking exhaust into the intake manifold, an EGR valve that is allowing too much flow (because the EGR differential pressure sensor that monitors EGR flow is faulty and is under-reporting EGR flow). If bad enough, a lean fuel condition may cause lean misfire, a rough idle, hesitation or stumble when accelerating, and/or poor engine performance. WHAT A LEAN CODE MEANSA lean fuel condition may exist if the engine is sucking in too much air and/or the fuel system is not delivering enough fuel.
This code is not set on four cylinder engines (no bank 2). IF the vehicle is driven long enough, typically both codes will be set.Ī P0171 lean code for bank 1 is the cylinder bank on the RIGHT (passenger) side of the engine on Ford vehicles with a V6 or V8 engine and rear-wheel drive.Ī P0174 lean code for bank 2 is the cylinder bank on the LEFT (driver) side of the engine on Ford vehicles with a transverse-mounted V6 engine and front-wheel drive. When the Check Engine Light comes on, either one of these codes, or both, may be found when a code reader or scan tool is plugged into the vehicle diagnostic connector. These codes commonly occur on many Ford vehicles, and are set when the powertrain control module (PCM) sees the air/fuel mixture is running too lean (too much air, not enough fuel).
#Ol fault 2003 mazda 6 p0171 manuals#
Auto Repair Library, Auto Parts, Accessories, Tools, Manuals & Books, Car BLOG, Links, Indexįord P0171 & P0174 Lean Codes by Larry Carley copyright 2019 Ī Ford P0171 is a LEAN code for cylinder bank 1, and P0174 is a LEAN code for cylinder bank 2.
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